Investigations will be carried out to define the underlying basis for the absence of enzyme activity that occurs in human and dog GMl gangliosidosis. These invesigations will include purification of beta-galactosidase A to homogeneity in quantities sufficient for structural studies (fingerpainting) and under purification conditions whereby the protein is obtained in an unaltered state. The procedure for purification which will be relied heavily upon is that of affinity chromatography. Subsequent to the purification, investigations will be carried out to determine whether structurally altered and enzymically inactive proteins are present in the patient's tissue which are immunologically similar to the normal proteins. The mutant beta-galactosidases will be isolated by affinity chromatography and characterized to determine the nature of the mutation at the protein level. Human mutants (normal with Hex A(minus); AB (plus)) of Hex A will be characterized to determine the nature of the mutation (Km, synthesis defect) in each, using substrate specificity studies with GM2 and immunological studies with specific anti-alpha chain and anti-beta chain antibodies.